Polystyrene foam has been used for some time as packing material, insulation material, structural materials and other various uses. Polystyrene foams exhibit many useful qualities in a wide variety of fields. The foams usefulness is based partly on its cost effectiveness, its inherent insulating qualities and the ease with which it may be formed into a great variety of shapes. For instance, the food handling industry has found polystyrene foam packaging to be of great use in the packaging of food products for its consumers. In addition, the building industry has found a large variety of uses for the foam. The chief concern for the various uses of the foam has been the amount of waste that is generated by the use of polystyrene foam products.
Generally speaking, polystyrene foam has primarily caused great concern because of its lack of biodegradability. The foam by its very nature takes up a great deal of volume per weight, which has caused many individuals to question its overall commercial usefulness when compared to the overall possible detrimental environmental impact. The environmental impact includes the accelerated rate that landfill space is being used up at because the foam, in its useful form, takes a large amount of space per weight of waste. Moreover, the transportation of the foam waste is very inefficient due to the volume weight ratio. Typically, the waste material is transported from a restaurant facility to a waste area. This transportation usually involves motor vehicle transport. The vehicles can transport a much greater weight of refuse than can be placed in the vehicle due to the large volume the polystyrene foam takes up. Therefore, the transportation of polystyrene foam products in general is very inefficient because the full capacity of the shipping means is not utilized.
Also, in the industry it has been very difficult to find an effective method of recycling the polystyrene foam products. This is due in part to the shipping cost described above and the cost of the process of the actual recycling. There is a therefore a continued need for a polystyrene foam volume reduction method to allow use of more conventional plastic recycling and processing equipment. At the present, very expensive and specialized processing equipment and extra polystyrene foam compaction steps are required to recycle polystyrene foam products.
One approach to the recycling of polystyrene foam is to use chemicals to reduce the foam. The basic problem in the industry, however, is that the chemicals that are often considered the most obvious to use are very toxic to the environment with the result that they are often banned by environmental legislation or regulations. One chemical series, pinene and terpenes such as d-limonene can reduce the foam volume. This approach is interesting but unfortunately it fails to be an effective method in some cases. Specifically, the cost of d-limonene is directly related to the crop levels of citrus products. Accordingly, when there is a problem with the production of citrus-based products due to bad growing conditions, it directly effects the price to recycle foam products to the point where it may no longer be cost effective.
Moreover, prior approaches evidence an inconsistent activity in collapsing polystyrene foams that has not previously been addressed in the industry. For example, while heat activation of the terpenes has removed this problem (U.S. Pat. No. 5,223,543, the entire contents of which are incorporated herein by reference), it adds to the overall cost of recycling and it involves a volatile environmentally compromising chemical. The chemicals used in the '543 patent were problematic for shipping due to their flash point. They are highly volatile and therefore extra precautions have to be taken when shipping such products that ultimately make use of such chemicals cost-ineffective. Moreover, the process used in the '543 patent was basically vapor phase, providing for possible emissions of vapors which were a Clean Air Act Problem. Thus there continues to be a major need for a polystyrene foam reduction process that uses low volatility agents.
Also, the use of volatile chemicals presents another problem for the recycling efforts of polystyrene foam products. The chemicals used heretofore suffer great loss in the recycling process due to evaporation. This makes the recycling materials vary hard to recover to be used again in the recycling process. As such, it greatly increases the cost to the recycling efforts. The evaporated chemicals would also potentially increase the danger of an accident during the recycling process due to unacceptable flash points of the chemicals. This is especially true were the best performance of the chemicals is aided by the application of heat to the recycling process. Ultimately, the volatile chemicals and heat required lead to conditions during the recycling process that are potentially very dangerous.
An ideal process would have little need for the heat activation step of U.S. Pat. No. 5,223,543 and would further allow viscous and higher boiling point materials to be employed. Ideally, these materials would not require longer residence times prior to recycling. A long time would delay the sequence of breaking down the polystyrene foam products and shipping of same. This increase in residence times adds to the overall cost of the recycling process. Also, the need to decrease residence time must be balanced with reduced heat activation in combination with higher boiling point materials whose combination would result in a heretofore unobtainable efficient and safe chemical reactant. In addition, it would be most desirable to have the product or sludge of the polystyrene foam collapsing reactions safely shippable. It would also be advantageous to identify effective compounds that insulate the polystyrene foam reducer market from the wide price variation of the orange crop related d-limonene market.
Also, it would be desirable to have a compound that is environmentally friendly. Part of the major problem with the past use of foam products is that they now occupy a great deal of space in our landfills. Therefore, there is a significant need for an agent that can be used at these landfills on foam, which has already been deposited into landfills. The only way to accomplish this is by the application of a foam reducing agent that has no detrimental side effects on the environment.
In a prior effort to address some of these needs, Katz et al. were recently issued U.S. Pat. No. 6,743,828 which is directed to a polystyrene foam reduction agent consisting of dibasic esters and a process using a liquid contact with polystyrene foam wherein the higher boiling temperature of the dibasic esters and contact with the liquid provides a volume reduction process and less evaporation loss as well as safer transportation of the chemicals and the polystyrene in its reduced state. The foam reduction agent consisting of dibasic esters and the process employed results in a reduced sludge that is also recyclable to superior quality raw polystyrene foam beads and the reduction agents are recoverable for future use.
In addition to the use of the dibasic esters to reduce the volume of polystyrene foam or expanded polystyrene foam (EPS), traditional methods used in the normal course of reducing and/or recycling polystyrene foam or expanded polystyrene foam (EPS) typically involve the use of significant ancillary equipment including, but not limited to, thin film evaporators (TFEs), and/or machines commonly referred to in the art as “fluffers”. Even if the temperature is considered low in the art, the TFE and/or fluffer time factors come into play and in the normal course of processing this results in a burning of the polystyrene foam or expanded polystyrene foam. It would therefore be beneficial in the processing stage for the polystyrene foam or expanded polystyrene foam to have a short residence time so as to shorten the thermal history of the polystyrene. The beaded polystyrene end product of such a process would be of higher quality and would be less likely to degrade.
Notwithstanding the usefulness of the prior polystyrene foam reduction recycling systems using dibasic or dialkyl esters, there is a continuing need in the art to develop other more versatile polystyrene foam reduction recycling systems to enhance the efficiency and full range of recycling possibilities. This invention solves these and other long felt needs by providing compositions and methods utilizing dibasic esters, low vapor pressure dibasic esters or functional derivatives thereof in combination with one or more extruders in a polystyrene foam reduction recycling system.